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Numeric Data Types

Numeric Data Types. There are six numeric data types: byte , short , int , long , float , and double . Sample variable declarations: int i, j, k; float numberOne, numberTwo; long bigInteger; double bigNumber;. Data Type Precisions.

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Numeric Data Types

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  1. Numeric Data Types • There are six numeric data types: byte, short, int, long, float, and double. • Sample variable declarations: int i, j, k; float numberOne, numberTwo; long bigInteger; double bigNumber;

  2. Data Type Precisions The six data types differ in the precision of values they can store in memory.

  3. int firstNumber, secondNumber; A. Variables are allocated in memory. firstNumber = 234; secondNumber = 87; firstNumber 234 secondNumber A int firstNumber, secondNumber; 87 firstNumber = 234; secondNumber = 87; B B. Values are assigned to variables. Primitive Data Declaration and Assignments int firstNumber, secondNumber; firstNumber = 234; secondNumber = 87; State of Memory Code

  4. number 237 35 A. The variable is allocated in memory. A int number; B number = 237; B. The value 237 is assigned to number. C number = 35; C. The value 35 overwrites the previous value 237. Assigning Numeric Data int number; number = 237; number = 35; int number; number = 237; number = 35; State of Memory Code

  5. Numeric Data Types • At the time a variable is declared, it also can be initialized. For example, we may initialize the integer variables count and height to 10 and 34 as int count = 10, height = 34; • Ping … out to reality … NumericVariables.java

  6. Numeric Literal Values • Integer types can be • Positive or negative • Decimal, e.g., -5653 • Octal, e.g., 05653 (but not 09876) • Hexidecimal, e.g., 0x5A1 • Long, e.g., 14084591234L • Real types can be • Float, e.g., 1.23f • Double, e.g., -2.34 • Scientific, e.g., 2.17e-27f or -456.2345e19

  7. This is an integer division where the fractional part is truncated. Arithmetic Operators • The following table summarizes the arithmetic operators available in Java. • ++ and -- for integer type variables

  8. Arithmetic Expressions • Examples: sum = firstNumber + secondNumber; avg = (one + two + three) / 3.0; total++; • Assignment operators, e.g., += /= etc. • Tral-la-la, out to reality … NumericOperators.java

  9. Arithmetic Expressions • How does the expression x + 3 * y get evaluated? Answer: x is added to 3*y. • We determine the order of evaluation by following the precedence rules. • A higher precedence operator is evaluated before the lower one. If two operators are the same precedence, then they are evaluated left to right for most operators.

  10. Precedence Rules

  11. Example • a * (b + -(c / d) / e) * (f - g % h) • a * -b - (d + e * f) * (-g + h) • a = 10; • b = 5; • c = 23; • d = 4; • e = 2; • f = 5; • g = 8; • h = 3;

  12. Example Program • Flonk … out to reality … NumericPrecedence.java

  13. Type Casting • If x is a float and y is an int, what will be the data type of the following expression? x * y The answer is float. • The above expression is called a mixed expression. • The data types of the operands in mixed expressions are converted based on the promotion rules. The promotion rules ensure that the data type of the expression will be the same as the data type of an operand whose type has the highest precision.

  14. Promotion Rules

  15. Assignment Conversion • If a lower precision value is assigned to a higher precision variable, type casting occurs • Example double number; number = 25; is legal but int number; number = 23.45; is not

  16. Type case x to float and then divide it by 3. Type cast the result of the expression x / y * 3.0 to int. Explicit Type Casting • Instead of relying on the promotion rules, we can make an explicit type cast by prefixing the operand with the data type using the following syntax: ( <data type> ) <expression> • Example (float) x / 3 (int) (x / y * 3.0)

  17. Example Program • Fuuuurtang … out to reality … NumericCasting.java

  18. The reserved word final is used to declare constants. These are constants, also called named constant. These are called literal constant. Constants • We can change the value of a variable. If we want the value to remain the same, we use a constant. final double PI = 3.14159; final int MONTH_IN_YEAR = 12; final short FARADAY_CONSTANT = 23060;

  19. Use of Constants • Very often class variables that are initialized • May be private or public • Local and instance variables may be declared final so they can be assigned a value only once • Yabbadabba … out to reality … FinalVariables.java

  20. The Math Class • The Math class in the java.lang package includes many common and useful mathematical functions such sin, cos, tan, square root, exponentiation, and others. • The mathematical formula is expressed in Java as Math.abs( Math.sin( Math.PI / 4.0) * x ) • Splodge … out to reality … MathFunctions.java

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